1. Field of the Invention
The present invention relates to an improved electrical circuit for driving a complex AC load from a DC source, and more particularly, to such an electrical circuit including an inverter and a high-reactance transformer in circuit with a closed-loop feedback control for producing, from a low, DC input voltage, a controlled high-voltage AC output.
2. Description of the Prior Art
To produce high-voltage AC for driving a complex load, that is a load comprising a resistor in parallel with a stray capacitance, such that the output voltage has a controlled and repeatable rise time, the usual method is to drive a conventional high-voltage transformer from a two-transistor AC inverter. Such an inverter operates at the desired output frequency, which may be 400-600 Hz, typically, and the output voltage magnitude is controlled by adjusting the DC voltage applied to the input of the inverter. Such usually requires a separate control circuit. Because of the inherent leakage reactance resulting from the magnetics of the high-reactance, high-voltage transformer, combined with the stray capacitance of the high-voltage coil and the load, a natural L-C tank circuit is formed. This L-C tank tends to "ring" or self-oscillate causing high peak output voltages and poor crest factor. The high peak to average ratio thus formed tends to increase the chance of random breakdown or arcing. The usual solution to minimize the effect of this L-C tank is to add a large bleeder to the output. Such a bleeder, however, is costly and consumes substantial power.
It is desirable to eliminate the use of such a bleeder as well as the DC pre-regulator in such a circuit for producing a high-voltage AC output.
It is an object of the present invention, therefore, to provide such an electrical circuit for producing a high-voltage AC output from a low-voltage DC input and which eliminates the use of a bleeder as well as a DC pre-regulator.
It is a further object of the present invention to provide such an electrical circuit whereby the unavoidable L-C components of the high-reactance transformer are used to best advantage in the circuit.